Device and process for the lining of a pipe branch, particuarly in an oil well

ABSTRACT

The device includes a radially deformable flexible tubular preform (1) that can be expanded by internal pressure and hardened in situ by heating its wall to polymerize it, the preform is formed of a rectilinear main section (10 and a rectilinear secondary section (11) at an acute angle (α) to the main section (10) and joined and sealed to the latter in a middle area (10c), temporary restraining bindings being provided to hold the secondary section initially in a radially folded condition, pressed against the main section (10), the combination then constituting a rectilinear preform, whereas after removal of the temporary restraining bindings (3), and due to internal pressure, the secondary section (11) separates from the main section (10), the combination then constituting a generally &#34;y&#34; shape preform adapted to be polymerized in the area of bifurcation of the well.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a device and a process for lining abifurcation in a well, particularly in an oil well.

2. Description of Related Art

The invention finds a particular application in sealing and lining thearea where a main bore that is generally (although not necessarily)vertical joins an oblique bore running from the vertical bore, known inthe art as a "side track".

This type of secondary bore is used to access lateral oil-bearingreservoirs when the main reservoir is exhausted or has become uneconomicor simply to increase the productivity of the well.

This type of bore also enables the production area to be significantlyexpanded into areas where access is difficult without having to drill anew well from the surface; this applies in particular to production fromdeposits under the sea.

Prior art processes use metal tubes to consolidate and seal theborehole, both for the main well and often for the secondary wells, andit is difficult to obtain a good seal in the area of the join.

It has already been proposed to line a well by means of an initiallyflexible radially deformable tubular preform that can be expanded byinternal pressure and hardened in situ by heating its wall to polymerizeit.

This technique is described in documents WO-94/21887 and WO-94/25655 andin unpublished French patent application 94 08691 of Jul. 7 1994, forexample.

The present invention proposes to transpose this technique known initself to lining the bifurcation area in which the main bore and thesecondary bore join.

BRIEF SUMMARY OF THE INVENTION

The objective of the invention is to propose a simple low-costlightweight device that is easy to put into place and produces a perfectseal of the junction in the bifurcation area.

The device for lining a bifurcation in a well, in particular in an oilwell, in accordance with the present invention comprises--in a mannerthat is known in itself--a radially deformable flexible tubular preformthat can be expanded by internal pressure and hardened in situ byheating its wall to polymerize it. The device is remarkable in that saidpreform is formed of a rectilinear main section and a rectilinearsecondary section at an acute angle to the main section and joined andsealed to the latter in a middle area, temporary restraining means beingprovided to hold the secondary section initially in a radially foldedcondition, pressed against the main section, the combination thenconstituting a rectilinear preform, whereas after removal of saidtemporary restraining means, and due to internal pressure, the secondarysection separates from the main section, the combination thenconstituting a generally "y" shape preform (the bottom bar of which isaligned with one of the top bars).

In accordance with a number of further, non-limiting features of theinvention:

the device includes an expander tool in the form of an inflatableflexible and elastic membrane bag housed inside the preform and adaptedto be pulled out at the end of operation.

in the expanded state each section has a circular cross-section, thediameter of the main section being greater than or the same as that ofthe secondary section.

said restraining means are breakable annular bindings around the mainand secondary sections adapted to break one after the other beyond aparticular internal pressure threshold.

The process for lining and sealing a bifurcation in a well, inparticular in an oil well, comprising a main bore and an obliquesecondary bore by means of a device as described hereinabove isremarkable in that, using a preform in which the angle between said mainsection and said secondary section is close to that of the bifurcation:

a) the preform is lowered into the well when in the radially retractedstate and with the secondary section pressed against the main section,the combination having a rectilinear configuration;

b) the preform is positioned in the area of the bifurcation so that thefree end of the secondary section is at the entry of the obliquesecondary bore;

c) the preform is inflated at moderate pressure (pre-inflation) so as torupture progressively the restraining bindings and to cause progressiveradial unfolding and angular deployment of the secondary sectionconcomitantly with further lowering of the preform;

d) lowering is stopped when the bifurcate portion of the preform issubstantially positioned at the level of the bifurcate portion of thewell;

e) the preform is inflated by increasing its internal pressure to causeit to expand radially and to press it against the walls of the well;

f) with the pressure maintained, the preform is heated to polymerize thewall;

g) the bag is deflated and separated from the preform.

Other features and advantages of the invention will become apparent fromthe description and the appended drawings which show by way ofnon-limiting example one embodiment and one preferred use of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a general view of the preform in its initial state, before itis introduced into the well;

FIGS. 2, 3 and 4 are views similar to FIG. 1 showing a plurality ofsuccessive steps of deployment of the preform during putting it intoplace;

FIGS. 5A, 5B, 5C are sections of the preform taken along the respectivelines A--A in FIG. 1, B--B in FIG. 1 and C--C in FIG. 4,

FIG. 6 is a schematic general view showing in longitudinal section abifurcation in a well into which a preform for lining said bifurcationhas been introduced;

FIGS. 7 through 16 are viewed analogous to FIG. 6, to a larger scale,showing the various steps of the lining process, the preform being shownin longitudinal section in FIGS. 11 through 16.

DETAILED DESCRIPTION OF THE INVENTION

In its normal state, which is that shown in FIG. 4, the preform 1 thatconstitutes the essential part of the device of the invention is aflexible preform that can be folded on itself longitudinally to occupy asmall overall radial size and can first be made round by a moderateinternal pressure and then expended radially by a higher internalpressure.

This principle of two-stage expansion, i.e. unfolding followed byexpansion, is described in WO-94/25655 already cited, for example (seeFIGS. 6A or 6B, 7 and 7').

In accordance with the present invention, the preform 1 includes arectilinear main section 10 and a secondary section 11 at an acute angleto the main section and joined to the latter in its middle area.

The preform is therefore the general shape of an inverted "y" with thebifurcation directed downwards, i.e. towards the bottom of the well.

The branch 10a of the main section is towards the mouth of the well andthe other branch 10b faces towards the bottom of the well, this branchfacing the secondary section 11.

The branches 10a and 10b have respective lengths La and Lb between 3 mand 5 m and the secondary section 11 has a length L in the order of 2 mto 4 m.

In the unfolded state the tubular sections 10 and 11 are cylindrical inshape, for example, the main section 10 has an outside diameter in theorder of 100 mm and an inside diameter in the order of 50 mm and thesection 11 has an outside diameter in the range 80 mm to 100 mm and aninside diameter in the range 30 mm to 50 mm.

The diameters are of course related directly to the diameters of thetubing in the well.

The angle α is in the order of 30°, for example.

The preform 1 and the internal expander tool, which is described in moredetail below, are fixed at the upper end of the preform to a tool 2fastened to the end of a cable, flexible tube or appropriate tooling 20,the opposite end of which exits the well through the well head.

Apparatus at the well head lowers the tube 20 into the well to bring thepreform into the required position, the cable, tube or tooling and thetool 2 being removed at the end of the operation, as is well known inthe art.

The tubular preform 1 has a multilayer structure that generally includesan outer skin and an inner skin between which is confined a resin thatcan be hardened by heat and is initially flexible and malleable.

With no internal pressure the part 10 can be folded longitudinally to agenerally heart-shaped section, as shown in FIG. 5A.

This shaping provides a place for the section 11 which, also by beingdeformed, can be pressed intimately against the section 10b so that thetwo sections in contact are inscribed within an imaginary cylinderextending the section 10a axially (see FIGS. 1 and 5A).

The preform is held in its folded condition and compressed by means of aseries of regularly spaced annular restraining bindings 3. These areglassfiber cables, for example.

The bindings have a tensile strength that increases progressively fromthe bottom upwards, for example, the bottom binding breaking more easilythan the binding above it, and so on, up to the top binding, which isnear the area 10c where the section 11 joins the main section.

FIG. 6 shows the bifurcate well to be tubed in section. It comprises amain bore 4, often vertical, fitted with cylindrical metal tubing 40,and an oblique bore 5 also provided with metal tubing 50, surrounded bycement 51.

The area 6 where the two bores join is surrounded by soil 60 and it ishere that the sealing problem arises, given that the tubing 40 and thetubing 50 are not joined together.

The device of the invention includes, mounted inside the preform 1, anexpanded tool in the form of an inflatable bag with a flexible andelastic membrane into the interior of which it is possible to introducea fluid under pressure, either from the well head or by pumping theliquid present in the well--for example water or oil--the pressure ofwhich can be varied and monitored.

This type of preform/expander tool combination is already described indetail in the previously mentioned WO-94/25655, to which reference maybe had as required, and for this reason will not be described again herein detail, as this would burden the description unnecessarily.

Referring to FIG. 11, the bag is constituted by the membrane 7 intowhich the tool 2 opens and which is closed off at its bottom end. Thebag has the shape of an inverted "y", complementary to its housinginside the preform.

The preform has a wall 8 of material that can be hardened by heating it.

Referring again to FIG. 6, which shows the start of the liningoperation, note that the preform 1 suspended from the tool 2 and fromthe cable, tube or tooling 20 has been lowered into the well so that the"closed" free end 110 of the secondary section 11 is in the bifurcationarea 6, substantially at the mouth of the secondary bore 5.

The preform moves easily in the well because it has a rectilinearconfiguration and a small overall size in the radial direction.

This position is shown in FIG. 7.

By introducing a fluid at moderate pressure, not exceeding a particularlimiting value, into the interior of the bag/preform combination, aninitial pre-inflation of the preform is achieved, the effect of which isfirst to break the lowest binding 3 (the weakest one).

At the same time, the preform is lowered a little further into the well.

By virtue of the first binding breaking, the bottom end areas of thesection 10b and the section 11 assume a cylindrical shape and the part11 tends to separate from the part 10b, being deployed laterally, totake up an angle to the part 10b. This movement, associated with otherorientation means, enables it to orient itself substantially on the axisof the secondary bore 5 (see FIG. 8).

The bindings 3 break in succession, from the bottom upwards,concomitantly with the lowering of the preform 1, the branch 10bdescending vertically and coaxially in the main bore 4 and the section11 penetrating axially into the secondary bore 5 (see FIG. 9).

When--as shown in FIG. 10--the middle area of the preform 10c reachesthe bifurcation area 6, the main section 10 and the secondary section 11of the preform being substantially aligned with the main bore 4 and thesecondary bore 5, respectively, lowering of the preform is stopped. Inthis state, the preform is still at a moderate pressure P₀ (FIG. 10).

The same situation is shown in FIG. 11, which shows the expandablebag/preform combination in section.

The fluid pressure inside the bag 7 is then increased to a value Psignificantly greater than P₀.

This causes inflation and progressive radial expansion from its middlearea of the whole of the preform, as shown in FIGS. 12, 13 and 14.

At the end of inflation, the top and bottom ends of the main section ofthe preform are pressed intimately against the tubing 40; likewise, thefree end area of the secondary section 11 is pressed intimately againstthe tubing 50.

The middle area of the preform is necessarily in contact with the wall60, but this is of no importance.

Then, in the conventional manner as described in WO-94/25655 alreadycited, for example, the preform is heated to polymerize it. This can bedone by introducing a hot liquid into the interior of the preform, forexample, or by chemical reaction or by the Joule effect, electricallyconductive wires being embedded in the wall of the preform and/or themembrane of the expander tool.

After polymerization, the preform is rigid and the required tubing isobtained in the form of an inverted "y" shape pipe that is perfectlysealed and connects the tubing 40 and the tubing 50.

As shown in FIG. 15, the bag 7 is then deflated by pumping out theliquid in it and then said bag is pulled out by pulling out the tool 2and the deflated bag attached to it.

FIG. 16 shows the lining as installed.

Note that the drawings (artificially) ignore the reduction in length ofthe sections of the preform that results from their radial expansion andwhich in practise is relatively great, with a view to facilitating anunderstanding of the various steps of the process.

The restraining means could consist of a woven material sheath that canbe torn longitudinally, from the bottom upwards, surrounding the preformparts 10b and 11.

The internal pressures P₀ and P are in fact differential pressuresbetween the pressures inside and outside the preform.

For example, P₀ is less than or equal to approximately 3 bars and P isin the order of 30 bars.

Again by way of example, if the initial--unfolded but notexpanded--diameter of the section 10 is in the order of 100 mm, it is inthe order of 160 mm after radial expansion.

It goes without saying that the dimensions of each of the sections 10and 11 and the value of the angle α are chosen to suit the actualconditions encountered in the field, in particular according to thediameter of the main and secondary bores and the angle between the twobores.

A device in which the preform consists of a main section with two oreven more than two auxiliary sections is within the scope of theinvention.

Similarly, the device of the invention can be used to seal and toconsolidate bifurcations in pipes.

We claim:
 1. A device for lining a bifurcation in a well, comprising:aradially deformable flexible tubular preform that can be expanded byinternal pressure and hardened by heating its wall to polymerize it,said preform having a rectilinear main section and a rectilinearsecondary section at an acute angle to the main section and joined andsealed to the latter in a middle area; temporary restraining means tohold the secondary section initially in a radially folded condition,pressed against the main section, the combination then constituting arectilinear preform, wherein after removal of said temporary restrainingmeans, and due to internal pressure, the secondary section separatesfrom the main section, the combination then constituting a generally "y"shape preform; and an expander tool in the form of an inflatableflexible and elastic membrane bag housed inside the preform and adaptedto be pulled out at the end of operation.
 2. A device according to claim1 wherein in the expanded state each section has a circularcross-section, the diameter of the main section being greater than orthe same as that of the secondary section.
 3. A device according toclaim 1 wherein said restraining means are breakable annular bindingsaround the main and secondary sections adapted to break one after theother beyond a particular internal pressure threshold.
 4. A deviceaccording to claim 1, wherein said well includes an oil well.
 5. Adevice according to claim 1, wherein said device is used in a pipe.
 6. Amethod for lining and sealing a bifurcation in a well having a main boreand an oblique secondary bore by using a preform in which the anglebetween a main section and a secondary section of the preform is closeto that of the bifurcation, said method comprising:a) lowering saidpreform into the well when in a radially retracted state and with thesecondary section pressed against the main section, the combinationhaving a rectilinear configuration; b) positioning the preform in thearea of the bifurcation so that a free end of the secondary section isat the entry of the oblique bore; c) inflating said preform at amoderate pressure so as to rupture progressively restraining bindingsand to cause progressive radial unfolding and angular deployment of thesecondary section concomitantly with further lowering of the preform; d)lowering is stopped when the bifurcate portion of the preform issubstantially positioned at the level of the bifurcate portion of thewell; e) further inflating said preform by increasing its internalpressure to cause it to expand radially and to press it against thewalls of the well; f) with the increased internal pressure maintained,heating the preform to polymerize the wall; g) deflating and separatingan expander tool from the preform.
 7. The method according to claim 6,wherein said well includes an oil well.